Water accessibility assessment (WAA) is very important to the ecological restoration of freshwater wetlands and water resources management due to an intensive human disturbance. This paper develops a quantitative methodology for WAA in the Yellow River Delta National Nature Reserve (YRDNNR), from which an assessment of water accessibility is made on the freshwater wetlands. The assessment uses a Water accessibility index (WAI) model by employing GIS network analysis and spatial statistical analysis. Five indicators for the model cover both natural and anthropogenic factors, including distance from freshwater resources, average elevation, road density, ditch density, and number of culverts at the grid scale. The values of the WAI model are between 0.26 and 0.82. The WAI has a significant and positive spatial autocorrelation. There are totally 12 freshwater marsh patches exist in the YRDNNR. The highest WAI value in the freshwater marsh patch occurs near the estuary area of the Yellow River, while the lowest WAI value lies farthest from the Yellow River. There are two freshwater restored wetlands that have lower WAI values, from which a scientific restoration strategy is presented to remove the paddy field, roads and other facilities between two wetlands and the Yellow River Course. The results of the WAI model have been validated by matching the ratio of water body area within patches and consulting with local administrators, which indicates a satisfied WAI assessment effectiveness. The proposed WAI can help administrators to guide wetland ecological restoration and to plan for freshwater resources management.